The long-term goal of this research is to understand the molecular basis of insecticide resistance in the cockroach. The cockroach is a major threat to human health as a carrier of human pathogens and a major source of indoor allergens and cause of acute asthma. Strategies for the control of cockroaches and other insect pests rely heavily on the application of insecticides. Pyrethroids are a large class of insecticides that possess high insecticidal activity and relative low mammalian toxicity. The heavy use of pyrethroids, however, led to rapid selection of resistant strains in many insect pest populations. Previous studies with the pyrethroid-resistant German cockroach strain, Ectiban- R, suggest that the pyrethroid resistance mechanism (kdr) in this strain is likely due to a mutation(s) in the para sodium channel gene. Recently cDNAs encoding para genes from Ectiban-R and a genetically related pyrethroid-susceptible strain, CSMA, have been cloned and sequenced. Sequence comparison reveals a single amino acid change, from L993 in ParaCSMA to F993 in ParaEctiban-R. The F993 mutation was found in most pyrethroid-resistant cockroach strains, some of which also possess additional kdr-associated para gene mutations. To characterize the effects of these kdr-associated para gene mutations on sodium channel properties and sodium channel interaction with pyrethroid insecticides, the following three specific aims are proposed: 1) Characterization of the responses of wild-type and mutant Para sodium channels to pyrethroids and site 2 neurotoxins; 2) Examination of functional properties of wild-type and mutant Para sodium channels; and 3) Characterization of pyrethroid binding to wild-type and mutant Para sodium channels. Knowledge gained from this project will have significant implications for preserving a whole class of pest control chemicals for the control of major urban insect pests and for further enhancing its efficacy through a better understanding of the molecular interactions between sodium channels and pyrethroids.